The invention relates generally to the filling of multiple tanks with a liquid, and more particularly to an automatic control method that governs the filling of multiple tanks with a liquid.
Filling or re-filling a ship""s fuel tanks is a process that can take place in port or at sea. In either case, the process of pumping a supply of fuel into the ship""s fuel tanks requires personnel to monitor a variety of flow rate, pressure and tank level sensors. The sensor outputs must then be evaluated and fuel flow rates must be adjusted in order to quickly and safely fill the fuel tanks without any unwanted pressure build-up and/or fuel overflow that results when fuel is pumped even after the fuel tanks have been filled to capacity. It is sometimes more difficult at sea to quickly and safely fill fuel tanks because sea state conditions can have an intermittent impact on tank levels.
Accordingly, it is an object of the present invention to provide a method of automatically controlling the filling of multiple tanks with a liquid.
Another object of the present invention is to provide a method of automatically controlling the filling of a ship""s fuel tanks.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a method is provided to automatically control the filling of a plurality of tanks with a liquid from a supply source. The tanks are equipped with an overflow sensing capability that detects an overflow condition indicative of the tanks being filled to capacity. A controllable valve is coupled to the supply source so that liquid dispensed therefrom must pass through the valve when the tanks are being filled. The valve has an increment associated therewith that defines how much the valve can be opened and closed when liquid is being dispensed therethrough. To start the filling process, the valve is opened to an initial position that defines a flow rate therethrough that falls within a prescribed range of acceptable flow rates. The liquid is then dispensed from the supply source through the controllable valve in its initial position. Each of (i) a flow rate of the liquid being dispensed, (ii) a level of the liquid in each of the tanks, and (iii) a state of the overflow sensor(s), is monitored and averaged over an amount of time. As a result, a corresponding (i) average flow rate, (ii) average level, and (iii) average state are defined. The valve is moved by its associated increment when the average flow rate is outside the range of acceptable flow rates. Specifically, the valve is closed by an amount equal to the increment when the average flow rate is greater than the range, and the valve is opened by an amount equal to the increment when the average flow rate is less than the range. Following each occurrence of a valve movement, a predetermined wait or delay time is implemented before further control processing takes place. The steps of monitoring/averaging, valve movement, and waiting after a valve movement, are repeated until one of a number of events occurs. A finalize filling process is initiated when one of these events occurs. These events include: (i) the average level being equal to a predetermined percentage of the capacity of the tanks, and (ii) the average state indicating the prescribed overflow condition. The finalize filling process fully closes the valve in accordance with a series of discrete movements thereof carried out over a specified time period.